Flange couplings being loaded with inner pressure or outer forces have a limited possibility for inspection and change of bolts without weakening the integrity of the coupling at the same time. Traditional clamps are difficult to adjust in such as way that a flange couplings gasket stress is held constant during transferal of forces from existing flange bolts and to the clamp. Typical equipment being used to preload flanged couplings is designed as described in U.S. Pat. No. 4,150,477 A1. By using such equipment to ensure constant gasket stress during bolt change, it is difficult to increase the pressure used on the tool to compensate exactly for the reduction in bolt forces during the unscrewing of the bolts. Likewise it is challenging to reduce the pressure used on the tool to compensate exactly for the increase in bolt forces during tightening of new bolts. Old corroded or cracked bolts suddenly tearing during unscrewing, presents further challenges related to the adjustment of the tool pressure to compensate for the loss of bolt force.